1. Field of the Invention
The present invention is in the fields of cell biology, immunology and oncology. The invention relates to the discovery that there is a relationship between the expression levels of the tumor suppressor gene smad4 (also known as dpc4) and integrin αvβ6, and the responsiveness of patient populations to αvβ6-active compounds and compositions (e.g., antibodies and other ligands that bind αvβ6), particularly in cancer cells from such patient populations, more particularly on carcinomas such as pancreatic carcinomas. The invention thus provides methods for determining the responsiveness of tumor cells (particularly those from pancreatic tumors) to such αvβ6-active compounds and compositions by examining the expression of αvβ6 and smad4 by the tumor cells, as well as methods of diagnosis and treatment/prevention of tumor progression using ligands, including antibodies and small molecule drugs, that bind to integrin αvβ6 on the surfaces of tumor cells and/or that block one or more components of the TGF-β pathway, particularly in smad4-deficient tumor cells.
2. Related Art
Integrins are cell surface glycoprotein receptors which bind extracellular matrix proteins and mediate cell-cell and cell-extracellular matrix interactions (generally referred to as cell adhesion events) (Ruoslahti, E., J. Clin. Invest. 87:1-5 (1991); Hynes, R. O., Cell 69:11-25 (1992)). These receptors are composed of noncovalently associated alpha (α) and beta (β) chains which combine to give a variety of heterodimeric proteins with distinct cellular and adhesive specificities (Albeda, S. M., Lab. Invest. 68:4-14 (1993)). Recent studies have implicated certain integrins in the regulation of a variety of cellular processes including cellular adhesion, migration, invasion, differentiation, proliferation, apoptosis and gene expression (Albeda, S. M., Lab. Invest. 68:4-14 (1993); Juliano, R., Cancer Met. Rev. 13:25-30 (1994); Ruoslahti, E. and Reed, J. C., Cell 77:477-478 (1994); and Ruoslahti, E. and Giancotti, F. G., Cancer Cells 1:119-126 (1989); Plow, Haas et al. 2000; van der Flier and Sonnenberg 2001).
The αvβ6 receptor is one member of a family of integrins that are expressed as cell surface heterodimeric proteins (Busk, M. et al., J. Biol. Chem. 267(9):5790-5796 (1992)). While the αv subunit can form a heterodimer with a variety of β subunits (β1, β3, β5, β6 and β8), the β6 subunit can only be expressed as a heterodimer with the αv subunit. The αvβ6 integrin is known to be a fibronectin-, latency associated peptide (LAP)- and tenascin C-binding cell surface receptor, interacting with the extracellular matrix through the RGD tripeptide binding sites thereon (Busk, M. et al., J. Biol. Chem. 267:5790-5796 (1992); Weinacker, A. et al., J. Biol. Chem. 269:6940-6948 (1994); Prieto, A. L. et al., Proc. Natl. Acad. Sci. USA 90:10154-10158 (1993)). Although the αvβ6 integrin was first identified and sequenced more than 10 years ago, the biological significance of αvβ6, especially in disease, is still under investigation. The expression of αvβ6 is restricted to epithelial cells where it is expressed at relatively low levels in healthy tissue and significantly upregulated during development, injury, and wound healing (Breuss, J. M. et al., J. Histochem. Cytochem. 41:1521-1527 (1993); Breuss, J. M. et al., J. Cell Sci. 108:2241-2251 (1995); Koivisto, L. et al., Cell Adhes. Communic. 7:245-257 (1999); Zambruno, G. et al., J. Cell Biol. 129(3):853-865 (1995); Hakkinen, L. et al., J. Histochem. Cytochem. 48(6):985-998 (2000)). An increasing number of recent reports demonstrate that αvβ6 is upregulated on cancers of epithelial origin, including colon carcinoma (Niu, J. et al, Int. J. Cancer 92:40-48 (2001); Bates, R. C. et al., J. Clin. Invest. 115:339-347 (2005)), ovarian cancer (Ahmed, N. et al., J. Cell. Biochem. 84:675-686 (2002); Ahmed, N. et al., J. Histochem. Cytochem. 50:1371-1379 (2002); Ahmed, N. et al., Carcinogen. 23:237-244 (2002)), squamous cell carcinoma (Koivisto, L. et al., Exp. Cell Res. 255:10-17 (2000); Xue, H. et al., Biochem. Biophys. Res. Comm. 288:610-618 (2001); Thomas, G. J. et al., J. Invest. Derinatol. 117:67-73 (2001); Thomas, G. J. et al., Int. J. Cancer 92:641-650 (2001); Ramos, D. M. et al., Matrix Biol. 21:297-307 (2002); (Agrez, M. et al., Br. J. Cancer 81:90-97 (1999); Hamidi, S. et al., Br. J. Cancer 82(8):1433-1440 (2000); Kawashima, A. et al., Pathol. Res. Pract. 99(2):57-64 (2003)), and breast cancer (Arihiro, K. et al., Breast Cancer 7:19-26 (2000)). It has also been reported that the cc subunit may be involved in tumor metastasis, and that blocking this subunit consequently may prevent metastasis (for review, see Imhof, B. A. et al., in: “Attempts to Understand Metastasis Formation I,” U. Günthert and W. Birchmeier, eds., Berlin: Springer-Verlag, pp. 195-203 (1996)).
The αvβ6 integrin may have multiple regulatory functions in tumor cell biology. Recent studies have demonstrated that the extracellular and cytoplasmic domains of the β6 subunit mediate different cellular activities. The extracellular and transmembrane domains have been shown to mediate TGF-β activation and adhesion (Sheppard, D., Cancer and Metastasis Rev. 24:395-402 (2005); Munger, J. S. et al., Cell 96:319-328 (1999)). The cytoplasmic domain of the β6 subunit contains a unique 11-amino acid sequence that is important in mediating αvβ6 regulated cell proliferation, MMP production, migration, and pro-survival (Li, X. et al., J. Biol. Chem. 278(43):41646-41653 (2003); Thomas, G. J. et al., J. Invest. Derm. 117(1):67-73 (2001); Thomas, G. J. et al., Br. J. Cancer 87(8):859-867 (2002); Janes, S. M. and Watt, F. M., J. Cell Biol 166(3):419-431 (2004)). The β6 subunit has been cloned, expressed and purified (Sheppard et al., U.S. Pat. No. 6,787,322 B2, the disclosure of which is incorporated herein by reference in its entirety), and function-blocking antibodies that selectively bind to the αvβ6 integrin have been reported (Weinreb et al., J. Biol. Chem. 279:17875-17877 (2004), the disclosure of which is incorporated herein by reference in its entirety). Antagonists of (αvβ6 (including certain monoclonal antibodies) have also been suggested as possible treatments for certain forms of acute lung injury and fibrosis (see U.S. Pat. No. 6,692,741 B2 and WO 99/07405, the disclosures of which are incorporated herein by reference in their entireties).
αvβ6 can bind to several ligands including fibronectin, tenascin, and the latency associated peptide-1 and -3 (LAP1 and LAP3), the N-terminal 278 amino acids of the latent precursor form of TGF-β1 through a direct interaction with an arginine-glycine-aspartate (“RGD”) motif (Busk, M. et al., J. Biol. Chew. 267(9):5790-5796 (1992); Yokosaki, Y. et al., J. Biol. Chem. 271(39):24144-24150 (1996); Huang, X. Z. et al., J. Cell. Sci. 111:2189-2195 (1998); Munger, J. S. et al., Cell 96:319-328 (1999)). The TGF-β cytokine is synthesized as a latent complex which has the N-terminal LAP non-covalently associated with the mature active C-terminal TGF-β cytokine. The latent TGF-β complex cannot bind to its cognate receptor and thus is not biologically active until converted to an active form (Barcellos-Hoff, M. H., J. Mamm. Gland Biol. 1(4):353-363 (1996); Gleizes, P. E. et al., Stem Cells 15(3):190-197 (1997); Munger, J. S. et al., Kid. Int. 51:1376-1382 (1997); Khalil, N., Microbes Infect. 1(15):1255-1263 (1999)). αvβ6 binding to LAP1 or LAP3 leads to activation of the latent precursor form of TGF-β1 and TGF-β3 (Munger, J. S. et al., Cell 96:319-328 (1999)), proposed as a result of a conformational change in the latent complex allowing TGF-β to bind to its receptor. Thus, upregulated expression of αvβ6 can lead to local activation of TGF-β which in turn can activate a cascade of downstream events.
The TGF-β1 cytokine is a pleiotropic growth factor that regulates cell proliferation, differentiation, and immune responses (Wahl, S. M., J. Exp. Med. 180:1587-1590 (1994); Massague, J., Annu. Rev. Biochem. 67:753-791 (1998); Chen, W. and Wahl, S. M., TGF-β: Receptors, Signaling Pathways and Autoimmunity, Basel: Karger, pp. 62-91 (2002); Thomas, D. A. and Massague, J., Cancer Cell 8:369-380 (2005)). The role that TGF-β1 plays in cancer is two-sided. TGF-β is recognized to tumor suppressor and growth inhibitory activity yet, many tumors evolve a resistance to growth suppressive activities of TGF-β1 (Yingling, J. M. et al., Nature Rev. Drug Discov. 3(12):1011-1022 (2004); Akhurst, R. J. et al., Trends Cell Biol. 11(11):S44-S51 (2001); Balmain, A. and Akhurst, R. J., Nature 428(6980):271-272 (2004)). In established tumors, TGF-β1 expression and activity has been implicated in promoting tumor survival, progression, and metastases (Akhurst, R. J. et al., Trends Cell Biol. 11(11):S44-S51 (2001); Muraoka, R. S. et al., J. Clin. Invest. 109(12):1551 (2002); Yang, Y. A. et al., J. Clin. Invest. 109(12):1607-1615 (2002)). This is postulated to be mediated by both autocrine and paracrine effects in the local tumor-stromal environment including the effects of TGF-β on immune surveillance, angiogenesis, and increased tumor interstitial pressure. Several studies have now shown the anti-tumor and anti-metastatic effects of inhibiting TGF-β1 (Akhurst, R. J., J. Clin. Invest. 109(12):1533-1536 (2002); Muraoka, R. S. et al., J. Clin. Invest. 109(12):1551 (2002); Yingling, J. M. et al., Nat. Rev. Drug Discov. 3(12):1011-1022 (2004); Yang, Y. A. et al., J. Clin. Invest. 109(12):1607-1615 (2002); Halder, S. K. et al., Neoplasia 7(5):509-521 (2005); Tyer, S. et al., Cancer Biol. Ther. 4(3):261-266 (2005)).
Increased expression of αvβ6 on tumors, particularly at the tumor-stromal interface, may reflect a unique mechanism for local activation of TGF-β1 and the ability to promote tumor survival, invasion, and metastasis. The high level of expression in human metastases infers a potential role for αvβ6 in establishing metastases which is consistent with previous reports that αvβ6 can mediate epithelial to mesenchymal transition, tumor cell invasion in vitro, and expression correlated with metastases in a mouse model (Bates, R. C. et al., J. Clin. Invest. 115(2):339-347 (2005); Thomas, G. J. et al., Br. J. Cancer 87(8):859-867 (2002); Morgan, M. R. et al., J. Biol. Chem. 279(25):26533-26539 (2004)). We have previously described the generation of potent and selective anti-αvβ6 monoclonal antibodies (mAbs) that bind to both the human and murine forms of αvβ6 and block the binding of αvβ6 to its ligands and αvβ6 mediated activation of TGF-β1 (Weinreb, P. H. et al., J. Biol. Chem. 279(17):17875-17887 (2004)).
The generation of potent and selective anti-αvβ6 monoclonal antibodies (mAbs) that bind to both the human and murine forms of αvβ6 and block the binding of αvβ6 to its ligands and αvβ6 mediated activation of TGF-β1 has been previously described (Weinreb, P. H. et al., J. Biol. Chem. 279(17):17875-17887 (2004); see also U.S. patent application Ser. No. 11/483,190 by Violette et al., entitled “Anti-αvβ6 Antibodies and Uses Thereof,” filed on Jul. 10, 2006, which is incorporated herein by reference in its entirety). As also described in PCT Publication WO 03/100033, herein incorporated in its entirety by reference, high affinity antibodies against αvβ6, including the identification and analysis of key amino acid residues in the complementary determining regions (CDRs) of such antibodies, were discovered and characterized. In particular, these high affinity antibodies (a) specifically bind to αvβ6; (b) inhibit the binding of αvβ6 to its ligand such as LAP, fibronectin, vitronectin, and tenascin with an IC50 value lower than that of 10D5 (International Patent Application Publication WO 99/07405); (c) block activation of TGF-β; (d) contain certain amino acid sequences in the CDRs that provide binding specificity to αvβ6; (e) specifically bind to the β6 subunit; and/or (f) recognize αvβ6 in immunostaining procedures, such as immunostaining of paraffin-embedded tissues.
WO 03/100033 also describes the discovery that antibodies that bind to αvβ6 can be grouped into biophysically distinct classes and subclasses. One class of antibodies exhibits the ability to block binding of a ligand (e.g., LAP) to αvβ6 (blockers). This class of antibodies can be further divided into subclasses of cation-dependent blockers and cation-independent blockers. Some of the cation-dependent blockers contain an arginine-glycine-aspartate (RGD) peptide sequence, whereas the cation-independent blockers do not contain an RGD sequence. Another class of antibodies exhibits the ability to bind to αvβ6 and yet does not block binding of αvβ6 to a ligand (nonblockers).
Furthermore, WO 03/100033 discloses antibodies comprising heavy chains and light chains whose complementarity determining regions (CDR) 1, 2 and 3 consist of certain amino acid sequences that provide binding specificity to αvβ6. WO 03/100033 also provides for antibodies that specifically bind to αvβ6 but do not inhibit the binding of αvβ6 to latency associated peptide (LAP) as well as antibodies that bind to the same epitope.
WO 03/100033 further discloses cells of hybridomas 6.1A8, 6.2B10, 6.3G9, 6.8G6, 6.2B1, 6.2A1, 6.2E5, 7.1G10, 7.7G5, and 7.1C5, isolated nucleic acids comprising a coding sequences and isolated polypeptides comprising amino acid sequences of the anti-αvβ6 antibodies. In particular, WO 03/100033 discloses anti-αvβ6 antibodies comprising heavy and light chain polypeptide sequences as antibodies produced by hybridomas 6.1A8, 6.3G9, 6.8G6, 6.2B1, 6.2B10, 6.2A1, 6.2E5, 7.1G10, 7.7G5, or 7.1C5. Several of the hybridomas were deposited at the American Type Culture Collection (“ATCC”; P.O. Box 1549, Manassas, Va. 20108, USA) under the Budapest Treaty. In particular, hybridoma clones 6.3G9 and 6.8G6 were deposited on Aug. 16, 2001, and have accession numbers ATCC PTA-3649 and PTA-3645, respectively. The murine antibodies produced by hybridomas 6.3G9 and 6.8G6 are being further explored in the present application for their potential development as humanized antibodies.
The murine monoclonal antibody 3G9 is a murine IgG1, kappa antibody isolated from the β6 integrin −/− mouse (Huang et al., J. Cell Biol. 133:921-928 (1996)) immunized with human soluble αvβ6. The 3G9 antibody specifically recognizes the αvβ6 integrin epitope which is expressed at upregulated levels during injury, fibrosis and cancer (see, e.g., Thomas et al., J. Invest. Dermatology 117:67-73 (2001); Brunton et al., Neoplasia 3: 215-226 (2001); Agrez et al., Int. J. Cancer 81:90-97 (1999); Breuss, J. Cell Science 108:2241-2251 (1995)). It does not bind to other αv integrins and is cross-reactive to both human and murine molecules. The murine monoclonal antibody 3G9 has been described to block the binding of αvβ6 to LAP as determined by blocking of ligand binding either to purified human soluble αvβ6 or to β6-expressing cells, thereby inhibiting the pro-fibrotic activity of TGF-β receptor activation (see WO 03/100033). It has also been shown to inhibit αvβ6-mediated activation of TGF-β with an IC50 value lower than one of the known αvβ6 antibodies, 10D5 (Huang et al., J. Cell Sci. 111:2189-2195 (1998)).
The murine monoclonal antibody 8G6 is a murine IgG1, kappa antibody which also recognizes the αvβ6 integrin epitope, as described in WO 03/100033. The murine monoclonal antibody 8G6 is a cation-dependent, high affinity blocker of αvβ6 displaying the ability to inhibit αvβ6—mediated activation of TGF-β with an IC50 value lower than 10D5 (see WO 03/100033).
Both the 3G9 and 8G6 murine antibodies were effective in preventing fibrosis of the kidney and lung, as described in WO 03/100033. Furthermore, the murine antibody 3G9 was able to effectively inhibit tumor growth in a human tumor xenograft model, suggesting the potential role of αvβ6 in cancer pathology and the effectiveness of such blockade using antibodies directed at αvβ6.
Smad4 is a component of the Smad pathway that is involved in signal transduction in the TGF-β pathway (Levy, L. and Hill, C. S., Molec. Cell. Biol. 25:8108-8125 (2005); Fukuchi, M. et al., Cancer 95:737-743 (2002)). This gene, also known as dpc4 (for “decreased in pancreatic carcinoma”), appears to be a tumor suppressor gene, and a decrease in smad4 expression has been observed in a variety of primary carcinomas, including pancreatic carcinomas (Luttges, J. et al., Am. J. Pathol. 158:1677-1683 (2001); Subramanian, G. et al., Cancer Res. 64:5200-5211 (2004)), esophageal carcinomas (Fukuchi, M. et al., Cancer 95:737-743 (2002), cervical carcinomas (Maliekal, T. T. et al., Oncogene 22:4889-4897 (2003), and other primary human cancers (Iacobuzio-Donahue, C. A. et al., Clin. Canc. Res. 10:1597-1604 (2004), as well as in cell line cancer models including of pancreatic cancers (Lohr, M. et al., Cancer Res. 61:550-555 (2001); Yasutome, M. et al., Clin. Exp. Metastasis 22:461-473 (2005)), and of colon cancers (Levy, L., and Hill, C. S., Molec. Cell. Biol. 25:8108-8125 (2005)). A reduced expression of smad4 in tumors has been associated with poor prognosis for patient survival, particularly in patients with smad-4-deficient pancreatic adenocarcinomas (Liu, F., Clin. Cancer Res. 7:3853-3856 (2001); Tascilar, M. et al., Clin. Cancer Res. 7:4115-4121 (2001); Toga, T. et al., Anticancer Res. 24:1173-1178 (2004)). The mechanism of the tumor suppressive activity of the smad4 gene product is poorly understood, but it is thought that it may act as a “switch” regulating the growth-suppressive and growth-activating activities of certain components of the TGF-β signaling pathway (for reviews, see Akhurst, A. J., J. Clin. Invest. 109:1533-1536 (2002); Bachman, K. E., and Park, B. H., Curr. Opin. Oncol. 17:49-54 (2004); Bierie, B., and Moses, H. L., Nature Rev. Cancer 6:506-520 (2006)).